U.S. patent application number 15/617482 was filed with the patent office on 2018-12-13 for process for metalization of copper pillars in the manufacture of microelectronics.
The applicant listed for this patent is MacDermid Enthone Inc.. Invention is credited to Jiang Chiang, John Commander, Tao Chi Liu, Elie Najjar, Thomas Richardson.
Application Number | 20180355502 15/617482 |
Document ID | / |
Family ID | 64562592 |
Filed Date | 2018-12-13 |
United States Patent
Application |
20180355502 |
Kind Code |
A1 |
Najjar; Elie ; et
al. |
December 13, 2018 |
PROCESS FOR METALIZATION OF COPPER PILLARS IN THE MANUFACTURE OF
MICROELECTRONICS
Abstract
Features such as bumps, pillars and/or vias can be plated best
using current with either a square wave or square wave with open
circuit wave form. Using the square wave or square wave with open
circuit wave forms of plating current, produces features such as
bumps, pillars, and vias with optimum shape and filling
characteristics. Specifically, vias are filled uniformly and
completely, and pillars are formed without rounded tops, bullet
shape, or waist curves. In the process, the metalizing substrate is
contacted with an electrolytic copper deposition composition. The
deposition composition comprises a source of copper ions, an acid
component selected from among an inorganic acid, an organic
sulfonic acid, and mixtures thereof, an accelerator, a suppressor,
a leveler, and chloride ions.
Inventors: |
Najjar; Elie; (Norwood,
MA) ; Commander; John; (Old Saybrook, CT) ;
Richardson; Thomas; (Killingworth, CT) ; Liu; Tao
Chi; (Zhubei City, TW) ; Chiang; Jiang;
(Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MacDermid Enthone Inc. |
Waterbury |
CT |
US |
|
|
Family ID: |
64562592 |
Appl. No.: |
15/617482 |
Filed: |
June 8, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/03452
20130101; H01L 2224/05017 20130101; H01L 2924/20753 20130101; H01L
2224/13005 20130101; H01L 2224/13082 20130101; H01L 2224/16227
20130101; H01L 23/5226 20130101; H01L 23/53228 20130101; H01L
2224/13111 20130101; H01L 24/05 20130101; H01L 2224/13147 20130101;
H01L 2924/2075 20130101; H01L 23/3114 20130101; H01L 2224/02311
20130101; H01L 2224/0579 20130101; H01L 21/76879 20130101; H01L
24/03 20130101; H01L 24/11 20130101; H01L 24/13 20130101; C25D
7/123 20130101; H01L 2224/0401 20130101; H01L 2224/0345 20130101;
H01L 2224/1147 20130101; H01L 2224/05647 20130101; H05K 999/99
20130101; H01L 2224/11462 20130101; C25D 3/38 20130101; H01L
2224/0569 20130101; H01L 2924/00015 20130101; H01L 21/2885
20130101; H01L 24/94 20130101; H01L 2924/20641 20130101; H01L 24/16
20130101; H01L 2924/381 20130101; H01L 2224/058 20130101; H01L
2224/13017 20130101; H01L 2924/20642 20130101; H01L 2924/20751
20130101; C25D 5/18 20130101; H01L 21/76898 20130101; H01L
2224/13023 20130101; H01L 2224/131 20130101; H01L 2224/94 20130101;
H01L 2924/20752 20130101; H01L 2924/3656 20130101; H01L 24/02
20130101; H01L 2224/0239 20130101; H01L 2224/11462 20130101; H01L
2924/00014 20130101; H01L 2224/13111 20130101; H01L 2924/01047
20130101; H01L 2224/13147 20130101; H01L 2924/00012 20130101; H01L
2224/0345 20130101; H01L 2924/00014 20130101; H01L 2224/05647
20130101; H01L 2924/00014 20130101; H01L 2224/0579 20130101; H01L
2924/00014 20130101; H01L 2224/058 20130101; H01L 2924/00014
20130101; H01L 2224/94 20130101; H01L 2224/03 20130101; H01L
2224/94 20130101; H01L 2224/11 20130101; H01L 2224/0569 20130101;
H01L 2924/07025 20130101; H01L 2924/0781 20130101; H01L 2224/0569
20130101; H01L 2924/07025 20130101; H01L 2224/0569 20130101; H01L
2924/0781 20130101; H01L 2224/13111 20130101; H01L 2924/01082
20130101; H01L 2224/13082 20130101; H01L 2224/13147 20130101; H01L
2224/13111 20130101; H01L 2924/01047 20130101; H01L 2224/13082
20130101; H01L 2224/13147 20130101; H01L 2224/13111 20130101; H01L
2924/01082 20130101; H01L 2924/00015 20130101; H01L 2224/13155
20130101; H01L 2924/00015 20130101; H01L 2224/13083 20130101; H01L
2224/0239 20130101; H01L 2924/01047 20130101; H01L 2224/03452
20130101; H01L 2924/00014 20130101; H01L 2224/131 20130101; H01L
2924/014 20130101 |
International
Class: |
C25D 7/12 20060101
C25D007/12; C25D 3/38 20060101 C25D003/38; C25D 5/02 20060101
C25D005/02; C25D 5/34 20060101 C25D005/34; H01L 21/288 20060101
H01L021/288; H01L 23/00 20060101 H01L023/00; H01L 21/768 20060101
H01L021/768; H01L 23/522 20060101 H01L023/522; H01L 23/532 20060101
H01L023/532 |
Claims
1. (canceled)
2. (canceled)
3. A process for forming an array of copper features on a
semiconductor substrate in wafer level packaging for
interconnecting an electronic circuit of a semiconductor device
with a circuit external to the device, the process comprising:
supplying current to an aqueous electrodeposition composition in
contact with a cathode comprising an array of under bump structures
on a semiconductor assembly, said aqueous electrodeposition
composition comprising a source of copper ions, an acid, an
accelerator, a suppressor, and a leveler; wherein an array of
copper pillars is electrodeposited on the array of under bump
structures comprising a seminal conductive layer for initiating the
electrodeposition of copper from the aqueous electrodeposition
composition; and wherein the current takes a form selected from the
group consisting of square wave and square wave with open circuit;
wherein each of the electrodeposited copper pillars within the
array of electrodeposited copper pillars has a height of from about
190 to 230 micrometers; wherein each of the electrodeposited copper
pillars within the array of electrodeposited copper pillars has a
within feature (WIF) percentage of 10 percent or less; and wherein
the rate of growth of the electrodeposited copper pillars within
the array of electrodeposited copper pillars in a vertical
direction from the seminal conductive layer is at least about 2.5
.mu.m/min.
4. (canceled)
5. A process as set forth in claim 3, wherein each of the under
bump structures is within a concavity comprising sidewalls.
6. A process as set forth in claim 5, wherein lateral growth of the
electrodeposited copper pillars during electrodeposition is
constrained by the sidewall(s) of the concavity.
7. (canceled)
8. A process as set forth in claim 3, wherein growth of a distal
end of the electrodeposited copper pillars is not laterally
constrained during electrodeposition.
9. (canceled)
10. A process as set forth in claim 3, wherein the seminal
conductive layer comprises a copper seed layer.
11. (canceled)
12. A process as set forth in claim 3, wherein the diameter of the
copper bump or pillars is between about 1 and about 30 .mu.m.
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. A process as set forth in claim 3, wherein each of the copper
pillars produced by the process has an aspect ratio of at least
about 1:1.
19. A process as set forth in claim 3, wherein each of the copper
pillars produced by the process has an aspect ratio between about
1:1 and about 6:1.
20. (canceled)
21. A process as set forth in claim 3, wherein each of the copper
pillars of said array of copper pillars is substantially equally
spaced from immediately neighboring pillars of the array.
22. (canceled)
23. A process as set forth in claim 3, wherein the array of
electrodeposited copper pillars has a within feature (WID)
uniformity of 10 percent or less.
24. A process as set forth in claim 3, wherein the source of copper
ions is copper sulfate.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to creating conductive features on
integrated circuit wafers such as vias, bumps and pillars using
copper electroplating. The invention is particularly suited to
plating vias that are relatively deep and/or have a relatively
small entry dimension.
[0002] Among the applications for the invention is the creation of
so-called "through silicon via" interconnections of integrated
circuit chips. The demand for semiconductor integrated circuit (IC)
devices such as computer chips with high circuit speed and high
circuit density requires the downward scaling of feature sizes in
ultra-large scale integration (ULSI) and very-large scale
integration (VLSI) structures. The trend to smaller device sizes
and increased circuit density requires decreasing the dimensions of
interconnect features and increasing their density. An interconnect
feature is a feature such as a via or trench formed in a dielectric
substrate which is then filled with metal, typically copper, to
yield an electrically conductive interconnect. Copper, having
better conductivity than any metal except silver, is the metal of
choice since copper metallization allows for smaller features and
uses less energy to pass electricity. In damascene processing,
interconnect features of semiconductor IC devices are metallized
using electrolytic copper deposition.
[0003] A patterned semiconductor integrated circuit device
substrate, for example, a device wafer or die, may comprise both
small and large interconnect features. Typically, a wafer has
layers of integrated circuitry, e.g., processors, programmable
devices, memory devices, and the like, built into a silicon
substrate. Integrated circuit (IC) devices have been manufactured
to contain small diameter vias and sub-micron sized trenches that
form electrical connections between layers of interconnect
structure. These features have dimensions on the order of about 150
nanometers or less, such as about 90 nanometers, 65 nanometers, or
even 45 nanometers.
[0004] Through silicon vias are critical components of
three-dimensional integrated circuits, and they can be found in RF
devices, MEMs, CMOS image sensors, Flash, DRAM, SRAM memories,
analog devices, and logic devices.
[0005] The depth of a TSV depends on the via type (via first or via
last), and the application. Via depth can vary from on the order of
about 20 microns to about 500 microns, typically between about 50
microns and about 250 microns or between about 25 and about 200
microns, e.g., between about 50 and about 125 microns. Via openings
in TSV have had entry dimensions, such as the diameter, on the
order of between about 200 nm to about 200 microns, such as between
about 1 and about 75 microns, e.g., between about 2 and about 20
microns. In certain highly dense integrated circuit chip
assemblies, the via entry dimension is preferably or necessarily
small, e.g., in the range of 2 micron to 20 microns.
[0006] Exemplary vias for which the process of the invention is
adapted would include 5.mu. wide.times.40.mu. deep, 5.mu.
wide.times.50.mu. deep, 6.mu. wide.times.60.mu. deep, and 8.mu.
wide.times.100.mu. deep. Thus, it may be seen that the process of
the invention is adapted for filling vias having an aspect ratio
>3:1, typically greater than 4:1, advantageously in the range
between about 3:1 and about 100:1 or between 3:1 and 50:1, more
typically in the range between about 4:1 and about 20:1, still more
typically in the range between about 5:1 and about 15:1. However,
it will be understood that the process is quite effective for
filling vias of distinctly lower aspect ratio, e.g., 3:1, 2:1, 1:1,
0.5:1 or even 0.25:1 or lower. Thus, while the novel process offers
particular advantages in the case of high aspect ratios, the
application of the process to filling lower aspect ratio vias is
fully within the contemplation of the invention.
[0007] In filling deep via, and especially deep vias with
relatively small entry dimensions, it has been found difficult to
maintain satisfactory deposition rates throughout the filling
process. As the extent of filling exceeds 50%, the deposition rate
typically declines, and the rate continues to drop as a function of
the extent of filling. The overburden may get thicker as a result.
In addition, due to the adsorption of the leveler onto the
sidewalls and bottom copper surface as discussed hereinbelow, the
impurities content of the deposit may also tend to increase. Deep
vias are also vulnerable to formation of seams and voids, a
tendency that may also be aggravated where entry dimension is small
and aspect ratio is high.
[0008] Further, to take advantage of the progressively finer and
denser architecture of integrated circuits, it is necessary to
provide corresponding ultra-miniaturization of semiconductor
packaging. Among the structural requirements for this purpose
include increases in the density of input/output transmission leads
in an integrated circuit chip.
[0009] In flip chip packaging, the leads comprise bumps or pillars
on a face of the chip, and more particularly on the side of the
chip that faces a substrate, such as a printed circuit board (PCB),
to which the circuitry of the chip is connected.
[0010] Input and output pads for flip chip circuitry are often
provided with solder bumps through which the pads are electrically
connected to circuitry external to the chip, such as the circuits
of a PCB or another integrated circuit chip. Solder bumps are
provided from relatively low melting point base metals and base
metal alloys comprising metals such as lead, tin, and bismuth.
Alloys of base metals with other electrically conductive metals,
such as Sn/Ag alloys are also used. In manufacture of the packaged
chip, the bumps are provided as globular molten beads on the
so-called under bump metal of the pad, and allowed to solidify in
place to form the electrical connector through which current is
exchanged between the chip and the external circuit. Unless
subjected to lateral or vertical constraint during solidification,
solder bumps generally assume a spherical form. As a consequence,
the cross-sectional area for current flow at the interface with the
under bump metal or pad may depend on the wettability of the under
bump structure by the solder bump composition. Absent external
constraints on the extent of lateral growth, the height of the bump
cannot exceed its lateral dimension, and is diminished relative to
the height as wettability of the under bump metal by the molten
solder increases. In short, dimensions of an unconstrained solder
bump are determined mainly by the surface tension of the molten
solder, the interfacial tension between the solder and the under
bump metal, and the extent to which the volume of the solder drop
can be controlled in operation of the solder delivery mechanism
used in the process.
[0011] In an array of solder bumps formed on the face of an
integrated circuit chip, these factors may limit the fineness of
the pitch, i.e., the distances between the centers of immediately
neighboring bumps in the array.
[0012] In order to achieve a finer pitch, attempts have been made
to substitute copper bumps or pillars for the solder by
electrodeposition onto the under bump metal. However, it can be
difficult to control the electrodeposition process to provide a
copper pillar of the desired configuration. While the shape of the
main body of the pillar can be determined by forming it within the
confines of a cavity having sidewalls formed from a dielectric
material, the configuration of the distal end of the pillar may
still be unsatisfactory, e.g., excessively domed, excessively
dished, or irregular.
[0013] By comparison with the provision of solder bumps,
manufacturing of copper pillars can suffer a further disadvantage
in productivity, and in the effect of productivity on manufacturing
cost. While a drop of molten solder can be delivered almost
instantaneously once a delivery head is brought into registry with
the under bump metal, the rate of electrodeposition of a copper
pillar is limited by the maximum current density that can be
achieved in the electrodeposition circuit. In commercial practice,
the current density is limited by various configuration problems,
including the problems of doming, dishing, and irregular
configuration at the distal end of a copper pillar, which are
aggravated if the current density rises above a limiting value, for
example, about 40 A/dm.sup.2, depending on the application,
corresponding to a vertical growth rate of no greater than about 7
.mu.m/min.
[0014] Although copper bumps and pillars have substantial
advantages over tin/lead solder bumps, a small bead of solder is
still used in the manufacturing process to bond the end of the bump
or pillar to external circuitry such as the circuit traces of a
PCB. However, to assure proper bonding of copper to the solder, and
to prevent formation of Kirkendall voids at the copper/solder
interface that may result from migration of copper into the solder
phase, it has been necessary to provide a nickel cap on the distal
end of the bump or pillar as a barrier between the copper phase and
the solder phase, thus adding to the expense and complication of
the manufacturing process.
[0015] Plating chemistry sufficient to copper metallize these
features has been developed and finds use in the copper damascene
method. Copper damascene metallization relies on superfilling
additives, i.e., a combination of additives that are referred to in
the art as accelerators, levelers, and suppressors. These additives
act in conjunction in a manner that can flawlessly fill copper into
the interconnect features (often called "superfilling" or "bottom
up" growth). See, for example, Too et al., U.S. Pat. No. 6,776,893,
Paneccasio et al., U.S. Pat. No. 7,303,992, and Commander et al.,
U.S. Pat. No. 7,316,772, the disclosures of which are hereby
incorporated as if set forth in their entireties.
SUMMARY OF THE INVENTION
[0016] Briefly, the invention is directed to a process for
electroplating features such as vias, bumps and/or pillars in a
semiconductor integrated circuit device. The integrated circuit
device comprises a surface having features therein. If a via, the
via feature comprises a sidewall extending from said surface, and a
bottom. The sidewall, bottom and said surface have a metalizing
substrate thereon for deposition of copper. The via feature has an
entry dimension between 1 micrometers and 25 micrometers, a depth
dimension between 50 micrometers and 300 micrometers, and an aspect
ratio greater than about 2:1. If a pillar, the process of this
invention can create pillars of heights up to 230 micrometers,
typically from 190 to 230 micrometers. The metalizing substrate
comprises a seed layer and is a cathode for electrolytic deposition
of copper thereon. In the process, the metalizing substrate is
contacted with an electrolytic copper deposition composition. The
deposition composition comprises a source of copper ions, an acid
component selected from among an inorganic acid, an organic
sulfonic acid, and mixtures thereof, an accelerator, a suppressor,
a leveler, and chloride ions. An electrodeposition circuit is
established comprising an anode, the electrolytic composition, the
aforesaid cathode, and a power source. A potential is applied
between the anode and the cathode to create electrodeposition
current causing reduction of copper ions at the cathode, thereby
plating copper onto the metallizing substrate at the bottom and
sidewall of the via, the via preferentially plating on the bottom
and lower sidewall to cause filling of the via from the bottom with
copper, or otherwise creating the bump or pillar.
[0017] The invention is further directed to a process for
metalizing a through silicon via feature in a semiconductor
integrated circuit device. The device comprises a surface having a
via feature therein, the via feature comprising a sidewall
extending from said surface, and a bottom. The sidewall, bottom and
said surface have a metalizing substrate thereon for deposition of
copper. The via feature has an entry dimension between 1
micrometers and 25 micrometers, a depth dimension between 50
micrometers and 300 micrometers, and an aspect ratio greater than
about 2:1, preferably between 4:1 and 20:1. If a pillar, the
process of this invention can create pillars of heights up to 230
micrometers, typically from 190 to 230 micrometers, measured from
top to bottom of the pillar. The metalizing substrate comprises a
seed layer and provides a cathode for electrolytic deposition of
copper thereon. In the process, the metalizing substrate is
contacted with an electrolytic copper deposition composition. The
deposition composition comprises a source of copper ions, an acid
component selected from among an inorganic acid, an organic
sulfonic acid, and mixtures thereof, an accelerator, a suppressor,
a leveler, and chloride ions. An electrodeposition circuit is
established comprising an anode, the electrolytic composition, the
aforesaid cathode, and a power source. A potential is applied
between the anode and the cathode during a via filling cycle to
generate a cathodic electrodeposition current causing reduction of
copper ions at the cathode, thereby plating copper onto the
metallizing substrate at the bottom and sidewall of the via, the
via preferentially plating on the bottom and lower sidewall to
cause filling of the via from the bottom with copper.
[0018] The inventors here have found that the features such as
bumps, pillars and/or vias can be plated best using current with
either a square wave or square wave with open circuit wave form. A
square wave consists of applying a forward current density of X
amps/sq dm for a predetermined period followed by another current
density of Y amps/sq dm for a predetermined period of time,
followed by a third current density of X.sup.1 amps/sq dm, followed
by a fourth current density of Y.sup.1 amps/sq dm, and then
optionally repeating the foregoing cycle, wherein X and X.sup.1 can
be the same or different values and Y and Y.sup.1 can be the same
or different values but X and Y must be different values of forward
current density. A square wave with open circuit wave form is the
same as a square wave, except that the current density is reduced
to zero at points within the plating cycle for predetermined
periods of time. The inventors here have determined that using the
square wave or square wave with open circuit wave forms produces
features such as bumps, pillars, and vias with optimum shape and
filling characteristics. Specifically, vias are filled uniformly
and completely, pillars are formed without rounded tops, bullet
shape, waist curves.
[0019] Other features will be in part apparent and in part pointed
out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic of a pillar with a bullet shape
showing a TIR measurement.
[0021] FIG. 2 is a photograph of a pillar with a bullet shape and
with a waist curve.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] In the electrodeposition of copper onto a metalizing
substrate, the accelerator, suppressor, and leveler components of
the electrolytic bath co-operate to promote bottom filling of a via
or creation of the bump or pillar.
[0023] If a via is present, the via feature comprises a sidewall
extending from said surface, and a bottom. The sidewall, bottom and
said surface have a metalizing substrate thereon for deposition of
copper. The via feature has an entry dimension between 1
micrometers and 25 micrometers, a depth dimension between 50
micrometers and 300 micrometers, and an aspect ratio greater than
about 2:1. If a pillar, the process of this invention can create
pillars of heights up to 230 micrometers, typically from 190 to 230
micrometers, measured from top to bottom of the pillar. The
metalizing substrate comprises a seed layer and is a cathode for
electrolytic deposition of copper thereon. In the process, the
metalizing substrate is contacted with an electrolytic copper
deposition composition. The deposition composition comprises a
source of copper ions, an acid component selected from among an
inorganic acid, an organic sulfonic acid, and mixtures thereof, an
accelerator, a suppressor, a leveler, and chloride ions. An
electrodeposition circuit is established comprising an anode, the
electrolytic composition, the aforesaid cathode, and a power
source. A potential is applied between the anode and the cathode to
create electrodeposition current causing reduction of copper ions
at the cathode, thereby plating copper onto the metallizing
substrate at the bottom and sidewall of the via, the via
preferentially plating on the bottom and lower sidewall to cause
filling of the via from the bottom with copper.
[0024] The invention is further directed to a process for
metalizing a through silicon via feature in a semiconductor
integrated circuit device. The device comprises a surface having a
via feature therein, the via feature comprising a sidewall
extending from said surface, and a bottom. The sidewall, bottom and
said surface have a metalizing substrate thereon for deposition of
copper. The via feature has an entry dimension between 1
micrometers and 25 micrometers, a depth dimension between 50
micrometers and 300 micrometers, and an aspect ratio greater than
about 2:1. The metalizing substrate comprises a seed layer and
provides a cathode for electrolytic deposition of copper thereon.
In the process, the metalizing substrate is contacted with an
electrolytic copper deposition composition. The deposition
composition comprises a source of copper ions, an acid component
selected from among an inorganic acid, an organic sulfonic acid,
and mixtures thereof, an accelerator, a suppressor, a leveler, and
chloride ions. An electrodeposition circuit is established
comprising an anode, the electrolytic composition, the aforesaid
cathode, and a power source. A potential is applied between the
anode and the cathode during a via filling cycle to generate a
cathodic electrodeposition current causing reduction of copper ions
at the cathode, thereby plating copper onto the metallizing
substrate at the bottom and sidewall of the via, the via
preferentially plating on the bottom and lower sidewall to cause
filling of the via from the bottom with copper.
[0025] In various preferred embodiments of the invention, as
described herein, a copper bump or pillar having a suitable distal
configuration is deposited at a relatively high rate of vertical
growth. By "suitable distal configuration" what is meant is that
the copper bump or pillar is not unduly domed, unduly dished, or
irregular in shape. The rate of growth of bumps and pillars having
suitable distal configurations compares favorably with the rate
that is achieved using electrodeposition baths that do not involve
the composition and process described herein.
[0026] The process described herein is useful for building copper
bumps and pillars in flip chip packaging and for other wafer-level
packaging features such as through silicon vias and redistribution
layers (RDLs) and processes directed to the manufacture of
integrated circuits. In wafer level packaging, an array of copper
bumps or pillars is provided over a semiconductor substrate for
interconnection of an electric circuit of a semiconductor device
with a circuit external to the device, for example, to a printed
circuit board (PCB) or another integrated chip circuit. Current is
supplied to the electrolytic solution while the solution is in
contact with a cathode comprising an under bump structure on a
semiconductor assembly. The semiconductor assembly comprises a base
structure bearing the under bump structure, and the latter
comprises a seminal conductive layer that may comprise either under
bump metal, which is preferably copper or a copper alloy, or an
under bump pad that comprises another conductive material such as,
for example, a conductive polymer. An under bump metal structure
may comprise, for example, a copper seed layer as provided by
physical vapor deposition.
[0027] In the electrodeposition of pillars, and optionally also in
the deposition of bumps, the under bump structure is positioned
within or extends into a concavity in the surface of the base
structure. The configuration of said bump or pillar is defined by
the complementary configuration of the concavity.
[0028] In one embodiment, the concavity comprises a floor
comprising the under bump pad or under bump metal and a sidewall
comprising a dielectric material. In another embodiment, the base
structure comprises a dielectric layer comprising a photoresist,
mask, or stress buffer material and the concavity comprises an
opening in a surface of the dielectric layer. In this instance, the
dielectric layer may be removed after electrodeposition of said
bump or pillar.
[0029] In addition, the sidewall of the concavity can be provided
with a dielectric liner prior to electrodeposition of the bump or
pillar. In other words, the cavity in which copper is to be
deposited may first be provided with a dielectric liner such as
silicon dioxide or silicon nitride. The dielectric liner can be
formed, for example, by chemical vapor deposition or plasma vapor
deposition. Alternatively, organic dielectrics can be used to
mitigate a coefficient of thermal expansion mismatch. A photoresist
wall of the cavity may have sufficient dielectric properties to
obviate the need for a further dielectric layer. However, the
nature of the vapor deposition process may cause a further
dielectric layer to form on the photoresist wall as well. A seminal
conductive layer is then provided by either chemical vapor
deposition of a seed layer.
[0030] In a process for forming bumps and pillars, the conductive
under bump structure may be deposited only at the bottom, i.e., the
floor, of the cavity, or in some embodiments, such as those
illustrated and described in U.S. Pat. No. 8,546,254 to Lu et al.,
the subject matter of which is herein incorporated by reference in
its entirety, the conductive under bump structure may extend from
the bottom of the concavity for some distance upwardly along the
sidewall. Preferably, at least the upper sidewall of the concavity
remains non-conductive. The bottom of the concavity can be flat, or
may comprise a recess filled with polyimide that promotes better
bonding. This embodiment of the process differs from filling TSVs,
for example, in which the seminal conductive layer is formed over
the entire surface of the cavity, including bottom and sidewalls,
and metallization is carried out to deposit copper on both bottom
and sidewalls.
[0031] In carrying out the process described herein, current is
supplied to an electrolytic circuit comprising a direct current
power source, the aqueous electrodeposition composition, an under
bump pad, under bump metal, or array of under bump pads or metal in
electrical communication with the negative terminal of the power
source and in contact with the electrodeposition composition, and
an anode in electrical communication with the positive terminal of
the power source and in contact with the electrodeposition
composition.
[0032] In wafer level packaging, under bump structures are arrayed
on a face of a semiconductor wafer, the under bump structure is
electrically connected to the negative terminal of the power
source, the semiconductor wafer and anode are immersed in the
electrodeposition bath, and the power applied. Using the
electrodeposition composition described herein within wafer (WIW)
uniformity is maintained at a standard deviation not greater than
about 10%, for example, while within die (WID) uniformity for dies
cut from the wafer is maintained at a standard deviation of, for
example, not greater than about 10%. Average feature (WIF) doming
is typically about 10%, for example, for baths containing a single
leveler. However, greater deviation may be tolerated in situations
where productivity gains can be achieved or the device has greater
tolerance of the deviation can be remedied downstream by, for
example, a mechanical copper removal process. Doming and dishing of
bumps and pillars can be minimized, and relatively flat head bumps
and pillars can be prepared, using electrodeposition baths
containing combinations of levelers as described herein.
[0033] The process can be used to provide the under bump metal pads
for flip chip manufacturing in which case the metalizing substrate
is generally limited to the faces of the bonding pads.
Alternatively, with reference to the under bump metal as the floor,
the process can be used to form a copper bump or pillar by
bottom-up filling of the cavity formed at its floor by the under
bump pad or under bump metal and on its sides by the sidewall of an
opening in a stress buffer layer and/or photoresist that allows
access to the pad or under bump metal. In the latter application,
the aperture size of the cavity is roughly comparable to that of a
blind through silicon via, and the parameters of the process for
building the bump or pillar are similar to those used for filling
blind TSVs. However, the concavity wall provided by openings in
photoresist or stress-reducing material is ordinarily not seeded
and is therefore non-conductive. Only a semiconductor or dielectric
under bump structure at the floor of the cavity is provided with a
seminal conductive layer, typically comprising a conductive polymer
such as a polyimide. In such embodiments, the process is not as
dependent on the balance of accelerator and suppressor as it is in
the case of bottom filling submicron vias or TSVs.
[0034] During the electrodeposition of a bump or pillar within a
concavity in the surface of the base structure, lateral growth
thereof is constrained by the sidewall(s) of the concavity, and the
configuration of the bump or pillar is defined by the complementary
configuration of the concavity.
[0035] In other embodiments, a bump may be grown over the under
bump metal or pad without lateral constraint, or may be caused to
grow above the upper rim of a concavity or other lateral
constraint, in which case a bump is formed that typically assumes a
generally spherical configuration. However, in these embodiments,
the configuration of the bump can be influenced by the orientation,
configuration and dimension of the anode in the electrolytic
circuit.
[0036] An anode immersed in an electrodeposition bath can be
brought into registry with an under bump structure that is also
immersed in the bath, or each of an array of anodes can be brought
into registry with a complementary array of under bump structures
within the bath, and current applied to deposit a bump or pillar on
the under bump structure. If growth of the bump is not constrained
by the sidewall of a concavity, or if application of current is
continued to a point that the growing bump extends outside the
concavity or other lateral constraint, growth of the distal end of
the bump assumes a spherical or hemispherical shape. The anode may
be pulled away from the substrate along the axis of the growing
bump, and the vertical rate of withdrawal of the anode from
substrate can affect the shape of distal end of the bump.
Generally, the faster the pulling rate, the higher the tangential
angle .theta. (theta) between a horizontal plane and the growing
bump at any given distance between the location of the plane and
the under bump metal or pad. The pulling rate is not necessarily
constant but, if desired, can be varied with deposition time or
extent of vertical growth. Alternatively, the under bump structure
can be pulled away from the anode instead of the anode being pulled
away from substrate. In addition to the pulling rate of the anode,
the voltage difference between the anode and the cathode (initially
the under bump structure and thereafter the growing bump) can also
affect the shape of the bump.
[0037] It has been found that, where a solder bump is added at the
distal end of a copper bump or pillar that has been formed by the
process described herein, the solder bump adheres seamlessly to the
copper with a minimum of Kirkendall voids. Thus a solder bump
constituted of a low melting alloy such as, for example, Sn/Ag or
Sn/Pb, can be directly applied to the copper pillar or bump without
need for a cap on the copper consisting of an intermediate layer of
nickel or Ni alloy. Also Kirkendall voids are substantially avoided
at the juncture between the copper bump or pillar and an under bump
metal.
[0038] It has further been shown that the use of the compositions
described herein provides a high level of within die and within
wafer uniformity in the deposition of arrays of copper bumps or
pillars on a wafer that has been provided with an array of under
bump structures as also described herein.
[0039] Using the levelers described herein, high current densities
can be established and maintained throughout the electrodeposition
process. Thus, the rate at which a bump or pillar may be caused to
grow in the vertical direction is at least about 0.25 .mu.m/min,
more typically at least about 2.5 or about 3 .mu.m/min, and even
more typically at least about 3.3 .mu.m/min. Achievable growth
rates range up to about 10 .mu.m/min or higher, equating to a
current density of at least about 1 A/dm.sup.2, at least about 12
A/dm.sup.2, or at least about 20 A/dm.sup.2, ranging up to about 30
A/dm.sup.2 or higher.
[0040] Although polymeric and oligomeric reaction products of
dipyridyl and a difunctional alkylating agent are highly effective
for promoting the deposition of copper bumps and pillars that are
free of Kirkendall voids, and for achieving favorable within die
(WID), within wafer (WIW) and within feature (WIF) metrics, there
is a tendency for pillars produced from the baths described herein
to have substantial doming, except in the case of N-benzyl
substituted polyethylene imine, wherein the distal end of a bump or
pillar is more typically dished.
[0041] While the foregoing discusses the invention primarily in the
context of embodiments involving bumps and pillars, the
compositions and methods have also been proven to be effective in
forming other WLP copper features including megabumps, through
silicon vias, and redistribution layers. The compositions and
processes also apply to heterogeneous WLPs and semiconductor
substrates other than Si-based substrates, such as, for example,
GaAs-based substrates.
[0042] Before immersion in the electrolytic plating bath, the
integrated chip or other microelectronic device is preferably
"pre-wet" with water or other solution in which the concentration
of leveler and suppressor is generally lower than the concentration
of these components in the electrolytic bath. Pre-wetting helps to
avoid introducing entrained air bubbles when the device is immersed
in the electrolytic bath. Pre-wetting may also be used to speed up
gap fill. For this purpose, the pre-wet solution may contain a
copper electrolyte, with or without additives. Alternatively, the
solution can contain only the accelerator component, or a
combination of all additives.
[0043] Preferably, the device is pre-wet with water, e.g., an
aqueous medium devoid of functional concentrations of active
components, most preferably deionized water. Thus, as the wetted
device is immersed in the electrolytic bath, the water film remains
as a diffusion layer (boundary layer) between the bulk electrolytic
solution and the metalizing substrate on the field (exterior) of
the device and within the via. For the electrolytic process to
function, copper ions must diffuse from the bulk solution through
the boundary layer to the metalizing substrate. Each other active
component, in order to provide its function, must also diffuse
through the boundary layer to the cathodic surface. Upon initial
immersion, diffusion commences and is driven by the concentration
gradient across the boundary layer. After potential is applied,
copper ions and other positively charged components are also driven
to the cathode by the electrical field. As the electrolytic process
proceeds and components of the bulk plating bath are drawn into the
boundary layer, the composition of the boundary layer changes, but
a relatively quiescent boundary layer is always present as a
barrier to mass transfer throughout the electrolytic process.
[0044] The accelerator is typically a relatively small organic
molecule that functions as an electron transfer agent and which
readily diffuses to and attaches itself to the metalizing substrate
even in the absence of an applied potential. Copper ions, which are
mobile and ordinarily present in the bath at substantially higher
concentrations than other components, also diffuse readily through
the boundary layer and contact the metalizing substrate. As a
cathodic potential is applied to the metalizing substrate,
diffusion of copper ions is accelerated under the influence of the
electrical field. Initially, the concentrations of suppressor and
leveler at the metalizing substrate and within the boundary layer
remain relatively low, especially within the via. At surfaces on
the exterior of the chip, mass transfer of suppressor and leveler
through the boundary layer is promoted by convection and typically
further promoted by agitation. But because the via is very small,
the extent of convection and the effect of agitation is mitigated,
so that transfer of suppressor and leveler to the copper surface
within the via is retarded relative to the rate of mass transfer of
these components to the metalizing substrate in the field or within
the upper reaches of the via. In effect, the entire content of the
via might be considered to constitute a boundary layer between the
bulk solution outside the via entry and the interior wall (sidewall
and bottom) of the via.
[0045] The deposition potential is also substantially influenced by
the degree of agitation, and more particularly by the extent of
turbulence or relative flow at the substrate surface. Higher
turbulence at, and/or relative flow along, the substrate has the
effect of requiring a more negative electrodeposition potential for
deposition of copper. Thus, at the surfaces that are influenced by
agitation, agitation suppresses the copper electrodeposition rate
by promoting adsorption of leveler and/or a suppressor from an
electrolytic bath containing these components. While turbulence and
relative flow tend to increase the mass transfer coefficients
across the boundary layer for all active components of the
electrolytic solution, agitation has a disproportionate effect on
the otherwise slow mass transfer of suppressor and leveler relative
to the comparatively rapid transfer of copper ions and accelerator,
i.e., agitation tends to promote mass transfer of suppressor and
leveler to a greater extent than copper ions and accelerator
because the copper ions and accelerator are small in size and
diffuse relatively rapidly under the influence of the electrical
field even in the absence of turbulence. As a consequence,
agitation of the electrolytic bath can enhance the selectivity of
electrodeposition.
[0046] Thus, where the electrolytic bath is agitated, the highest
turbulence or relative flow is on the substrate along the surface
of the integrated circuit device, with the degree of turbulence
decreasing with depth in the via. As a consequence of this gradient
of decreasing turbulence, agitation increases the slope of the
electrodeposition potential gradient from the top to the bottom of
the via, reinforcing the effect of the relative diffusivities of
copper ions and accelerator vs. suppressor and leveler in directing
the deposition process to begin at the bottom of a via and to
progress upwardly in an orderly manner until the via is filled.
[0047] Expressed in another way, the accelerated mass transfer of
leveler and suppressor to the cathodic surface along face of the
field and the upper regions of the via relative to the bottom of
the via, as induced by agitation, enhances the differential in
conductivity between the electrical path from anode to the bottom
of via vs. the electrical paths to the field and the upper regions
of the via. In other words, agitation enhances selectivity toward
bottom filling. Moreover, under the constant current condition that
is preferably maintained during any given phase of the deposition
process, enhanced selectivity also contributes to an increase in
the absolute current density at the bottom of the via, not merely
to an increase relative to the current density in the other
regions.
[0048] Typical leveler molecules have a molecular weight in the
range of about 100 g/mol to about 500,000 g/mol, for example.
Because of its size, the leveler diffuses very slowly,
significantly more slowly than the suppressor S. Its slow diffusion
rate coupled with its strong charge cause the leveler to
concentrate at the areas of the metalizing substrate at the surface
of the integrated circuit chip and the very top reaches of the via.
Where the leveler attaches to the substrate, it is not readily
displaced by either the accelerator A or the suppressor S. In
essence, the system is driven toward a phase equilbrium between the
electrolytic solution and the metalizing surface in which relative
concentration of leveler is much higher than accelerator or
suppressor at the surface. As a further consequence of its size and
charge, the leveler exhibits a strongly suppressive effect on
electrodeposition, requiring an even more negative
electrodeposition potential than that required by the presence of
the suppressor. As long as the leveler is concentrated at the
exterior surface (the field) of the chip (or other microelectronic
device) and the upper reaches of the via, it is effective to retard
electrodeposition on those surfaces, thereby minimizing undesirable
overburden and preventing pinching and formation of voids at or
near the via entry. Too high a concentration of leveler in the via
can substantially retard bottom up capability by redirecting the
current path of least resistance and thus increasing the plating
rate on the field relative to the bottom of the via and thus
compromising the desired bottom-up filling.
[0049] When electrodeposition is initiated, the leveler L does not
immediately reach a significant concentration in the boundary
layer. Under the influence of convection and agitation, it is
fairly readily drawn to the metalizing surface of the field, but
does not immediately penetrate the via to any significant extent.
However, as the filling cycle progresses, the slow-diffusing
leveler eventually works its way into the upper reaches of the via.
Since the via is preferentially filling from the bottom, the
presence of leveler near the top of the via does not present an
obstacle to the bottom-filling process; and at constant current in
the electrolytic circuit, adsorption of the leveler to the upper
regions of the via redirects current to the bottom of the via
thereby actually accelerating the filling rate at the bottom. As
the via progressively fills with copper, the leveler continues to
diffuse down the via. At locations where the leveler attaches to
the via sidewall and bottom up copper surface, a distinctly more
negative electrodeposition potential becomes required for copper
deposition. As electrodeposition proceeds, the filling level (i.e.,
the copper filling front) and the location to which the leveler
front has diffused progressively approach each other, as shown in
FIG. 1C. As the filling level and leveler front come into close
proximity, and especially as the leveler adsorbs to a significant
extent onto the upper surface of the copper filling the via (see
FIG. 1D), the inevitable result is a sharp decrease in the bottom
up speed, with current being redirected to the field, with the
further adverse effect of increasing copper overburden. As a
result, a distinctly higher applied potential is thereafter
required to drive the process forward, and under these
circumstances the copper deposition pattern resulting from forcing
the current is not favorable. At a given applied potential, the
bottom up deposition rate significantly declines and copper
deposition is redirected to the top surface, extending the
deposition cycle and starkly reducing the productivity of the via
filling process. Diffusion of leveler into the via retards the
bottom up process to the extent that it may take two hours or more
to complete filling of the via with copper, and thus increases the
overburden.
[0050] The inventors here have found that the features such as
bumps, pillars and/or vias can be plated best using current with
either a square wave or square wave with open circuit wave form. A
square wave consists of applying a forward current density of X
amps/sq dm for a predetermined period followed by another current
density of Y amps/sq dm for a predetermined period of time,
followed by a third current density of X.sup.1 amps/sq dm, followed
by a fourth current density of Y.sup.1 amps/sq dm, and then
optionally repeating the foregoing cycle, wherein X and X.sup.1 can
be the same or different values and Y and Y.sup.1 can be the same
or different values, but X and Y must be different values of
forward current density. A square wave with open circuit wave form
is the same as a square wave, except that the current density is
reduced to zero at points within the plating cycle for
predetermined periods of time. The inventors here have determined
that using the square wave or square wave with open circuit wave
forms produces features such as bumps, pillars, and vias with
optimum shape and filling characteristics. Specifically, vias are
filled uniformly and completely, pillars are formed without rounded
tops, bullet shape, waste curves.
[0051] Generally the current density in the forward current can be
progressively stepped up as the deposition process proceeds. At the
outset of the plating cycle, the cathode comprises only the seed
layer which is of limited conductivity and provides only a limited
surface for electrolytic current. Thus, as defined with reference
to the entire metalizing surface, the current is relatively low,
e.g., in the 0.5 to 1.5 mAkm.sup.2 range. During this initial lower
current density stage, copper deposition is generally conformal--in
contrast to "bottom-up"--as the thin and sometimes discontinuous
copper seed layer (having been pre-deposited by a non-electrolytic
process such as chemical vapor deposition or physical vapor
deposition, is converted to a continuous and thicker layer more
capable of carrying current associated with bottom-up filling. As
copper builds up and covers the metalizing substrate, thus
transforming the initial seed layer, the current density can be
significantly increased, thereby enhancing the rate of copper
deposition and accelerating the completion of the filling cycle
when functioning in concert with desorptive anodic intervals in
concert with the further compositional and process parameters
discussed hereinabove.
[0052] The process of the invention is applicable to the
manufacture of integrated circuit devices wherein the semiconductor
substrate may be, for example, a semiconductor wafer or chip. The
semiconductor substrate is typically a silicon wafer or silicon
chip, although other semiconductor materials, such as germanium,
silicon germanium, silicon carbide, silicon germanium carbide, and
gallium arsenide are applicable to the method of the present
invention. The semiconductor substrate may be a semiconductor wafer
or other bulk substrate that includes a layer of semiconductive
material. The substrates include not only silicon wafers (e.g.
monocrystalline silicon or polycrystalline silicon), but silicon on
insulator ("SOI") substrates, silicon on sapphire ("SOS")
substrates, silicon on glass ("SOG") substrates, epitaxial layers
of silicon on a base semiconductor foundation, and other
semiconductor materials, such as silicon-germanium, germanium,
ruby, quartz, sapphire, gallium arsenide, diamond, silicon carbide,
or indium phosphide.
[0053] The semiconductor substrate may have deposited thereon a
dielectric (insulative) film, such as, for example, silicon oxide
(SiO.sub.2), silicon nitride (SiN.sub.x), silicon oxynitride
(SiO.sub.xN.sub.y), carbon-doped silicon oxides, or low-K
dielectrics. Low-K dielectric refers to a material having a smaller
dielectric constant than silicon dioxide (dielectric constant=3.9),
such as about 3.5, about 3, about 2.5, about 2.2, or even about
2.0. LOW-.kappa. dielectric materials are desirable since such
materials exhibit reduced parasitic capacitance compared to the
same thickness of SiO.sub.2 dielectric, enabling increased feature
density, faster switching speeds, and lower heat dissipation.
Low-.kappa. dielectric materials can be categorized by type
(silicates, fluorosilicates and organo-silicates, organic polymeric
etc.) and by deposition technique (CVD; spin-on). Dielectric
constant reduction may be achieved by reducing polarizability, by
reducing density, or by introducing porosity. The dielectric layer
may be a silicon oxide layer, such as a layer of phosphorus
silicate glass ("PSG"), borosilicate glass ("BSG"),
borophosphosilicate glass ("BPSG"), fluorosilicate glass ("FSG"),
or spin-on dielectric ("SOD"). The dielectric layer may be formed
from silicon dioxide, silicon nitride, silicon oxynitride, BPSG,
PSG, BSG, FSG, a polyimide, benzocyclobutene, mixtures thereof, or
another nonconductive material as known in the art. In one
embodiment, the dielectric layer is a sandwich structure of
SiO.sub.2 and SiN, as known in the art. The dielectric layer may
have a thickness ranging from approximately 0.5 micrometers to 10
micrometers. The dielectric layer may be formed on the
semiconductor substrate by conventional techniques.
[0054] The electrolytic solution used in the process of the
invention is preferably acidic, i.e., having a pH less than 7.
Generally, the solution comprises a source of copper ions, a
counteranion for the copper ions, an acid, an accelerator, a
suppressor, and a leveler. Preferably, the source of copper ions is
copper sulfate or a copper salt of an alkylsulfonic acid such as,
e.g., methane sulfonic acid. The counteranion of the copper ions is
typically also the conjugate base of the acid, i.e., the
electrolytic solution may conveniently comprise copper sulfate and
sulfuric acid, copper mesylate and methane sulfonic acid, etc. The
concentration of the copper source is generally sufficient to
provide copper ion in a concentration from about 1 g/L copper ions
to about 80 g/L copper ions, more typically about 4 g/L to about
110 g/L copper ions. The source of sulfuric acid is typically
concentration sulfuric acid, but a dilute solution may be used. In
general, the source of sulfuric acid is sufficient to provide from
about 2 g/L sulfuric acid to about 225 g/L sulfuric acid in the
copper plating solution. In this regard, suitable copper sulfate
plating chemistries include high acid/low copper systems, low
acid/high copper systems, and mid acid/high copper systems. In high
acid/low copper systems, the copper ion concentration can be on the
order of 4 g/L to on the order of 30 g/L; and the acid
concentration may be sulfuric acid in an amount of greater than
about 100 g/L up to about 225 g/L. In one high acid/low copper
system, the copper ion concentration is about 17 g/L where the
H.sub.2SO.sub.4 concentration is about 180 g/L. In some low
acid/high copper systems, the copper ion concentration can be
between about 35 g/L and about 85 g/L, such as between about 25 g/L
and about 70 g/L. In some low acid/high copper systems, the copper
ion concentration can be between about 46 g/L and about 60 g/L,
such as between about 48 g/L and about 52 g/L. (35 g/L copper ion
corresponds to about 140 g/L CuSO.sub.4.5H.sub.2O copper sulfate
pentahydrate.) The acid concentration in these systems is
preferably less than about 100 g/L. In some low acid/high copper
systems, the acid concentration can be between about 5 g/L and
about 30 g/L, such as between about 10 g/L and about 15 g/L. In
some low acid/high copper, the acid concentration can be between
about 50 g/L and about 100 g/L, such as between about 75 g/L to
about 85 g/L. In an exemplary low acid/high copper system, the
copper ion concentration is about 40 g/L and the H.sub.2SO.sub.4
concentration is about 10 g/L. In another exemplary low acid/high
copper system, the copper ion concentration is about 50 g/L and the
H.sub.2SO.sub.4 concentration is about 80 g/L. In mid acid/high
copper systems, the copper ion concentration can be on the order of
30 g/L to on the order of 60 g/L; and the acid concentration may be
sulfuric acid in an amount of greater than about 50 g/L up to about
100 g/L. In one mid acid/high copper system, the copper ion
concentration is about 50 g/L where the H.sub.2SO.sub.4
concentration is about 80 g/L.
[0055] Another advantage of employing copper sulfate/sulfuric is
the deposited copper contained very low impurity concentrations. In
this regard, the copper metallization may contain elemental
impurities, such as carbon, sulfur, oxygen, nitrogen, and chloride
in ppm concentrations or less. For example, copper metallization
has been achieved having carbon impurity at concentrations of less
than about 50 ppm, less than 30 ppm, less than 20 ppm, or even less
than 15 ppm. Copper metallization has been achieved having oxygen
impurity at concentrations of less than about 50 ppm, less than 30
ppm, less than 20 ppm, less than 15 ppm, or even less than 10 ppm.
Copper metallization has been achieved having nitrogen impurity at
concentrations of less than about 10 ppm, less than 5 ppm, less
than 2 ppm, less than 1 ppm, or even less than 0.5 ppm. Copper
metallization has been achieved having chloride impurity at
concentrations of less than about 10 ppm, less than 5 ppm, less
than 2 ppm, less than 1 ppm, less than 0.5 ppm, or even less than
0.1 ppm. Copper metallization has been achieved having sulfur
impurity at concentrations of less than about 10 ppm, less than 5
ppm, less than 2 ppm, less than 1 ppm, or even less than 0.5
ppm.
[0056] The alternative use of copper methanesulfonate as the copper
source allows for greater concentrations of copper ions in the
electrolytic copper deposition composition in comparison to other
copper ion sources. Accordingly, the source of copper ion may be
added to achieve copper ion concentrations greater than about 50
g/L, greater than about 90 g/L, or even greater than about 100 g/L,
such as, for example about 110 g/L. Preferably, the copper methane
sulfonate is added to achieve a copper ion concentration between
about 70 g/L and about 100 g/L.
[0057] When copper methane sulfonate is used, it is preferred to
use methane sulfonic acid and its derivative and other organic
sulfonic acids as the electrolyte. When methane sulfonic acid is
added, its concentration may be between about 1 g/L and about 50
g/L, such as between about 5 g/L and about 25 g/L, such as about 20
g/L.
[0058] High copper concentrations in the bulk solution contribute
to a steep copper concentration gradient that enhances diffusion of
copper into the features. Experimental evidence to date indicates
that the copper concentration is optimally determined in view of
the aspect ratio of the feature to be copper metallized. For
example, in embodiments wherein the feature has a relatively low
aspect ratio, such as about 3:1, about 2.5:1, or about 2:1
(depth:opening diameter), or less, the concentration of the copper
ion is added and maintained at the higher end of the preferred
concentration range, such as between about 90 g/L and about 110
g/L, such as about 110 g/L. In embodiments wherein the feature has
a relatively high aspect ratio, such as about 4:1, about 5:1, or
about 6:1 (depth:opening diameter), or more, the concentration of
the copper ion may be added and maintained at the lower end of the
preferred concentration range, such as between about 50 g/L and
about 90 g/L, such as between about 50 g/L and 70 g/L. Without
being bound to a particular theory, it is thought that higher
concentrations of copper ion for use in metallizing high aspect
ratio features may increase the possibility of necking (which may
cause voids). Accordingly, in embodiments wherein the feature has a
relatively high aspect ratio, the concentration of the copper ion
is optimally decreased. Similarly, the copper concentration may be
increased in embodiments wherein the feature a relatively low
aspect ratio.
[0059] Chloride ion may also be used in the bath at a level up to
about 200 mg/L (about 200 ppm), preferably about 10 mg/L to about
90 mg/L (10 to 90 ppm), such as about 50 gm/L (about 50 ppm).
Chloride ion is added in these concentration ranges to enhance the
function of other bath additives. In particular, it has been
discovered that the addition of chloride ion enhances void-free
filling.
[0060] The accelerator component of the electrolytic bath
preferably comprises an water-soluble organic divalent sulfur
compound. A preferred class of accelerators has the following
general structure (1):
##STR00001##
wherein
[0061] X is O, S, or S.dbd.O;
[0062] n is 1 to 6;
[0063] M is hydrogen, alkali metal, or ammonium as needed to
satisfy the valence;
[0064] R.sub.1 is an alkylene or cyclic alkylene group of 1 to 8
carbon atoms, an aromatic hydrocarbon or an aliphatic aromatic
hydrocarbon of 6 to 12 carbon atoms; and
[0065] R.sub.2 is hydrogen, hydroxyalkyl having from 1 to 8 carbon
atoms, or MO.sub.3SR.sub.1 wherein M and R.sub.1 are as defined
above.
[0066] In certain preferred embodiments, X is sulfur, and n is 2,
such that the organic sulfur compound is an organic disulfide
compound. Preferred organic sulfur compounds of Structure (1) have
the following structure (2):
##STR00002##
wherein M is a counter ion possessing charge sufficient to balance
the negative charges on the oxygen atoms. M may be, for example,
protons, alkali metal ions such as sodium and potassium, or another
charge balancing cation such as ammonium or a quaternary amine.
[0067] One example of the organic sulfur compound of structure (2)
is the sodium salt of 3,3'-dithiobis(1-propanesulfonate), which has
the following structure (3):
##STR00003##
[0068] An especially preferred example of the organic sulfur
compound of structure (2) is 3,3'-dithiobis(1-propanesulfonic
acid), which has the following structure (4):
##STR00004##
[0069] Additional organic sulfur compounds that are applicable are
shown by structures (5) through (16):
##STR00005## ##STR00006## ##STR00007##
[0070] The concentration of the organic sulfur compound may range
from about 0.1 ppm to about 100 ppm, such as between about 0.5 ppm
to about 20 ppm, preferably between about 1 ppm and about 6 ppm,
more preferably between about 1 ppm and about 3 ppm, such as about
1.5 ppm.
[0071] As the suppressor component, the electrolytic copper plating
bath preferably comprises a polyether of relatively low moderately
high molecular weight, e.g., 200 to 50,000, typically 300 to
10,000, more typically 300 to 5,000. The polyether generally
comprises alkylene oxide repeat units, most typically ethylene
oxide (EO) repeat units, propylene oxide (PO) repeat units, or
combinations thereof. In those polymeric chains comprising both EO
and PO repeat units, the repeat units may be arranged in random,
alternating, or block configurations. The polymeric chains
comprising alkylene oxide repeat units may contain residues derived
from an initiating reagent used to initiate the polymerization
reaction. Compounds applicable for use in the this invention
include polypropylene glycol amine (PPGA), in particular
poly(propylene glycol)bis(2-aminopropyl ether) (400 g/mol) and low
molecular weight polypropylene glycol (PPG). As described, e.g., in
U.S. Pat. No. 6,776,893 which is expressly incorporated herein by
reference, a polyether suppressor may comprise a block copolymer of
polyoxyethylene and polyoxypropylene, a polyoxyethylene or
polyoxypropylene derivative of a polyhydric alcohol and a mixed
polyoxyethylene and polyoxypropylene derivative of a polyhydric
alcohol.
[0072] A preferred polyether suppressor compound as described in
U.S. Pat. No. 6,776,893 is a polyoxyethylene and polyoxypropylene
derivative of glycerine. One such example is propoxylated glycerine
having a molecular weight of about 700 g/mol. Another such compound
is EO/PO on glycerine having a molecular weight of about 2500
g/mol. Yet another example comprises an EO/PO polyether chain
comprising a naphthyl residue, wherein the polyether chain is
terminated with a sulfonate moiety. Such a material is available
under the trade designation Ralufon NAPE 14-00 from Raschig.
[0073] A suppressor may comprise a combination of propylene oxide
(PO) repeat units and ethylene oxide (EO) repeat units present in a
PO:EO ratio between about 1:9 and about 9:1 and bonded to a
nitrogen-containing species, wherein the molecular weight of the
suppressor compound is between about 1000 and about 30,000
Alternative suppressors are well known in the art.
[0074] The polyether polymer compound concentration may range from
about 1 ppm to about 1000 ppm, such as between about 5 ppm to about
200 ppm, preferably between about 10 ppm and about 100 ppm, more
preferably between about 10 ppm and about 50 ppm, such as between
about 10 ppm and about 20 ppm.
[0075] As the leveler, the electrolytic copper plating compositions
may further comprise a polymeric material comprising nitrogen
containing repeat units. It will be understood that other levelers
can be used, but nitrogenous polymeric levelers are preferred.
[0076] As a specific example, the leveler may comprise a reaction
product of benzyl chloride and hydroxyethyl polyethyleneimine. Such
a material may be formed by reacting benzyl chloride with a
hydroxyethyl polyethyleneimine that is available under the
tradename Lupasol SC 61B from BASF Corporation of Rensselear,
N.Y.). The hydroxyethyl polyethyleneimine has a molecular weight
generally in the range of 50,000 to about 160,000.
[0077] In some embodiments, the additive comprises vinyl-pyridine
based compounds. In one embodiment, the compound is a pyridinium
compound and, in particular, a quaternized pyridinium salt. A
pyridinium compound is a compound derived from pyridine in which
the nitrogen atom of the pyridine is protonated. A quaternized
pyridinium salt is distinct from pyridine, and quaternized
pyridinium salt-based polymers are distinct from pyridine-based
polymers, in that the nitrogen atom of the pyridine ring is
quaternized in the quaternized pyridinium salt and quaternized
pyridinium salt-based polymers. These compounds include derivatives
of a vinyl pyridine, such as derivatives of 2-vinyl pyridine,
3-vinyl pyridine, and, in certain preferred embodiments,
derivatives of 4-vinyl pyridine. The polymers of the invention
encompass homo-polymers of vinyl pyridine, co-polymers of vinyl
pyridine, quaternized salts of vinyl pyridine, and quaternized
salts of these homo-polymers and co-polymers.
[0078] Some specific examples of quaternized poly(4-vinyl pyridine)
include, for example, the reaction product of poly(4-vinyl
pyridine) with dimethyl sulfate, the reaction product of 4-vinyl
pyridine with 2-chloroethanol, the reaction product of 4-vinyl
pyridine with benzylchloride, the reaction product of 4-vinyl
pyridine with allyl chloride, the reaction product of 4-vinyl
pyridine with 4-chloromethylpyridine, the reaction product of
4-vinyl pyridine with 1,3-propane sultone, the reaction product of
4-vinyl pyridine with methyl tosylate, the reaction product of
4-vinyl pyridine with chloroacetone, the reaction product of
4-vinyl pyridine with 2-methoxyethoxymethylchloride, and the
reaction product of 4-vinyl pyridine with 2-chloroethylether.
[0079] Some examples of quaternized poly(2-vinyl pyridine) include,
for example, the reaction product of 2-vinyl pyridine with methyl
tosylate, the reaction product of 2-vinyl pyridine with dimethyl
sulfate, the reaction product of vinyl pyridine and a water soluble
initiator, poly(2-methyl-5-vinyl pyridine), and
1-methyl-4-vinylpyridinium trifluoromethyl sulfonate, among
others.
[0080] An example of a co-polymer is vinyl pyridine co-polymerized
with vinyl imidazole.
[0081] The molecular weight of the substituted pyridyl polymer
compound additives of the invention in one embodiment is on the
order of about 160,000 g/mol or less. While some higher molecular
weight compounds are difficult to dissolve into the electroplating
bath or to maintain in solution, other higher molecular weight
compounds are soluble due to the added solubilizing ability of the
quaternary nitrogen cation. The concept of solubility in this
context is reference to relative solubility, such as, for example,
greater than 60% soluble, or some other minimum solubility that is
effective under the circumstances. It is not a reference to
absolute solubility. The foregoing preference of 160,000 g/mol or
less in certain embodiments is not narrowly critical. In one
embodiment, the molecular weight of the substituted pyridyl polymer
compound additive is about 150,000 g/mol, or less. Preferably, the
molecular weight of the substituted pyridyl polymer compound
additive is at least about 500 g/mol. Accordingly, the molecular
weight of the substituted pyridyl polymer compound additive may be
between about 500 g/mol and about 150,000 g/mol, such as about 700
g/mol, about 1000 g/mol, and about 10,000 g/mol. The substituted
pyridyl polymers selected are soluble in the plating bath, retain
their functionality under electrolytic conditions, and do not yield
deleterious by-products under electrolytic conditions, at least
neither immediately nor shortly thereafter.
[0082] In those embodiments where the compound is a reaction
product of a vinyl pyridine or poly(vinyl pyridine), it is obtained
by causing a vinyl pyridine or poly(vinyl pyridine) to react with
an alkylating agent selected from among those which yield a product
which is soluble, bath compatible, and effective for leveling. In
one embodiment candidates are selected from among reaction products
obtained by causing vinyl pyridine or poly(vinyl pyridine) to react
with a compound of the following structure (17):
R.sub.1-L Structure (17)
wherein R.sub.1 is alkyl, alkenyl, aralkyl, heteroarylalkyl,
substituted alkyl, substituted alkenyl, substituted aralkyl, or
substituted heteroarylalkyl; and L is a leaving group.
[0083] A leaving group is any group that can be displaced from a
carbon atom. In general, weak bases are good leaving groups.
Exemplary leaving groups are halides, methyl sulfate, tosylates,
and the like.
[0084] In other embodiments, R.sub.1 is alkyl or substituted alkyl;
preferably, R.sub.1 is substituted or unsubstituted methyl, ethyl,
straight, branched or cyclic propyl, butyl, pentyl or hexyl; in one
embodiment R.sub.1 is methyl, hydroxyethyl, acetylmethyl,
chloroethoxyethyl or methoxyethoxymethyl.
[0085] In further embodiments, R.sub.1 is alkenyl; preferably,
R.sub.1 is vinyl, propenyl, straight or branched butenyl, straight,
branched or cyclic pentenyl or straight, branched, or cyclic
hexenyl; in one embodiment R.sub.1 is propenyl.
[0086] In yet additional embodiments, R.sub.1 is aralkyl or
substituted aralkyl; preferably, R.sub.1 is benzyl or substituted
benzyl, naphthylalkyl or substituted naphthylalkyl; in one
embodiment R1 is benzyl or naphthylmethyl.
[0087] In still other embodiments, R.sub.1 is heteroarylalkyl or
substituted heteroarylalkyl; preferably, R.sub.1 is pyridylalkyl;
particularly, R.sub.1 is pyridylmethyl.
[0088] In various embodiments, L is chloride, methyl sulfate
(CH.sub.3SO.sub.4.sup.-), octyl sulfate
(C.sub.8H.sub.18SO.sub.4.sup.-), trifluoromethanesulfonate
(CF.sub.3SO.sub.3.sup.-), tosylate (C.sub.7H.sub.7SO.sub.3.sup.-),
or chloroacetate (CH.sub.2ClC(O)O.sup.-); preferably, L is methyl
sulfate, chloride or tosylate.
Water soluble initiators can be used to prepare polymers of vinyl
pyridine, though they are not used in the currently preferred
embodiments or in the working examples. Exemplary water soluble
initiators are peroxides (e.g., hydrogen peroxide, benzoyl
peroxide, peroxybenzoic acid, etc.) and the like, and water soluble
azo initiators such as 4,4'-Azobis(4-cyanovaleric acid).
[0089] In a variety of embodiments, the leveler component comprises
a mixture of one of the above-described polymers with a quantity of
a monomer which is, for example, a monomeric vinyl pyridine
derivative compound. In one such embodiment, the mixture is
obtained by quaternizing a monomer to yield a quaternized salt
which then undergoes spontaneous polymerization. The quaternized
salt does not completely polymerize; rather, it yields a mixture of
the monomer and spontaneously generated polymer.
[0090] The compound may be prepared by quaternizing 4-vinyl
pyridine by reaction with dimethyl sulfate. Polymerization occurs
according to the following reaction scheme (45-65.degree. C.):
##STR00008##
[0091] The average molecular weight of the polymer is generally
less than 10,000 g/mol. The monomer fraction may be increased with
an increase in amount of methanol used in the quaternization
reaction; that is, the degree of spontaneous polymerization is
decreased.
[0092] In some embodiments, the composition may comprise compounds
comprising quaternized dipyridyls. In general, quaternized
dipyridyls are derived from the reaction between a dipyridyl
compound and an alkylating reagent. Although such a reaction scheme
is a common method of quaternizing dipyridyls, the compounds are
not limited to only those reaction products that are derived from
the reaction between a dipyridyl compound and an alkylating
reagent, but rather to any compound having the functionality
described herein below.
Dipyridyls that may be quaternized to prepare the levelers of the
present invention have the general structure (18):
##STR00009##
wherein R.sub.1 is a moiety that connects the pyridine rings. In
Structure (18), each line from R.sub.1 to one of the pyridine rings
denotes a bond between an atom in the R.sub.1 moiety and one of the
five carbon atoms of the pyridine ring. In some embodiments,
R.sub.1 denotes a single bond wherein one carbon atom from one of
the pyridine rings is directly bonded to one carbon atom from the
other pyridine ring.
[0093] In some embodiments, the R.sub.1 connection moiety may be an
alkyl chain, and the dipyridyl may have the general structure
(19):
##STR00010##
wherein h is an integer from 0 to 6, and R.sub.2 and R.sub.3 are
each independently selected from among hydrogen or a short alkyl
chain having from 1 to about 3 carbon atoms. In Structure (19),
each line from a carbon in the alkyl chain to one of the pyridine
rings denotes a bond between a carbon atom in the alkyl chain and
one of the five carbon atoms of the pyridine ring. In embodiments
wherein h is 0, the connecting moiety is a single bond, and one
carbon atom from one of the pyridine rings is directly bonded to
one carbon atom from the other pyridine ring. In certain preferred
embodiments, h is 2 or 3. In certain preferred embodiments, h is 2
or 3, and each R.sub.2 and R.sub.3 is hydrogen.
[0094] In some embodiments, the R.sub.1 connecting moiety may
contain a carbonyl, and the dipyridyl may have the general
structure (20):
##STR00011##
wherein i and j are integers from 0 to 6, and R.sub.4, R.sub.5,
R.sub.6, and R.sub.6 are each independently selected from among
hydrogen or a short alkyl chain having from 1 to about 3 carbon
atoms. In Structure (20), each line from a carbon in the connecting
moiety to one of the pyridine rings denotes a bond between the
carbon atom in the connecting moiety and one of the five carbon
atoms of the pyridine ring. In embodiments wherein i and j are both
0, the carbon atom of the carbonyl is directly bonded to one carbon
atom in each of the pyridine rings.
[0095] Two compounds in the general class of dipyridyls of
structure (20), in which i and j are both 0, are 2,2'-dipyridyl
ketone (structure (21)) and 4,4'-dipyridyl ketone (structure (22)),
having the structures shown below:
##STR00012##
In some embodiments, the R.sub.1 connecting moiety may contain an
amine, and the dipyridyl may have the general structure (23):
##STR00013##
wherein k and 1 are integers from 0 to 6, and R.sub.8, R.sub.9,
R.sub.10, R.sub.11, and R.sub.12 are each independently selected
from among hydrogen or a short alkyl chain having from 1 to about 3
carbon atoms. In Structure (23), each line from a carbon in the
connecting moiety to one of the pyridine rings denotes a bond
between the carbon atom in the connecting moiety and one of the
five carbon atoms of the pyridine ring. In embodiments wherein k
and 1 are both 0, the nitrogen is directly bonded to one carbon
atom in each of the pyridine rings.
[0096] One compound in the general class of dipyridyls of structure
(23), in which k and 1 are both 0 and R.sub.12 is hydrogen, is
dipyridin-4-ylamine having the structure (24) shown below:
##STR00014##
[0097] In some embodiments, the R.sub.1 connecting moiety comprises
another pyridine. Such a structure is actually a terpyridine having
the general structure (25):
##STR00015##
[0098] In this structure, each line from each pyridine ring denotes
a bond between one carbon on one ring and another carbon on another
ring.
[0099] One such compound in the general class compounds of
structure (25) is a terpyridine having the structure (26):
##STR00016##
[0100] Preferably, the dipyridyl is chosen from the general class
of dipyridyls of general structure (19), and further in which
R.sub.2 and R.sub.3 are each hydrogen. These dipyridyls have the
general structure (27):
##STR00017##
wherein in is an integer from 0 to 6. In Structure (27), each line
from a carbon atom in the alkyl chain to one of the pyridine rings
denotes a bond between a carbon atom in the alkyl chain and one of
the five carbon atoms of the pyridine ring. In embodiments wherein
m is 0, the connecting moiety is a single bond, and one carbon atom
from one of the pyridine rings is directly bonded to one carbon
atom from the other pyridine ring. In certain preferred
embodiments, m is 2 or 3.
[0101] Dipyridyls of the above general structure (27) include
2,2'-dipyridyl compounds, 3,3'-dipyridyl compounds, and
4,4'-dipyridyl compounds, as shown in the following structures
(28), (29), and (30), respectively:
##STR00018##
wherein m is an integer from 0 to 6. When m is 0, the two pyridine
rings are directly bonded to each other through a single bond. In
preferred embodiments, m is 2 or 3.
[0102] 2,2'-dipyridyl compounds include 2,2'-dipyridyl,
2,2'-ethylenedipyridine (1,2-Bis(2-pyridyl)ethane),
Bis(2-pyridyl)methane, 1,3-Bis(2-pyridyl)propane,
1,4-Bis(2-pyridyl)butane, 1,5-Bis(2-pyridyl)pentane, and
1,6-Bis(2-pyridyl)hexane.
[0103] 3,3'-dipyridyl compounds include 3,3'-dipyridyl,
3,3'-ethylenedipyridine (1,2-Bis(3-pyridyl)ethane),
Bis(3-pyridyl)methane, 1,3-Bis(3-pyridyl)propane,
1,4-Bis(3-pyridyebutane, 1,5-Bis(3-pyridyl)pentane, and
1,6-Bis(3-pyridyl)hexane.
[0104] 4,4'-dipyridyl compounds include, for example,
4,4'-dipyridyl, 4,4'-ethylenedipyridine (1,2-Bis(4-pyridyl)ethane),
Bis(4-pyridyl)methane, 1,3-Bis(4-pyridyl)propane,
1,4-Bis(4-pyridyl)butane, 1,5-Bis(4-pyridyl)pentane, and
1,6-Bis(4-pyridyl)hexane.
[0105] Of these dipyridyl compounds, 4,4'-dipyridyl compounds are
preferred since compounds based on 4,4'-dipyridyl have been found
to be particularly advantageous levelers in terms of achieving low
impurity inclusion and underplate and overplate reduction. In
particular, 4,4'-dipyridyl, having the structure (31),
4,4'-ethylenedipyridine, having structure (32), and
1,3-Bis(4-pyridyl)propane having structure (33) are more preferred.
Compounds based on the dipyridyls of structure (32) and (33) are
currently the most preferred levelers.
##STR00019##
[0106] These compounds are quaternized dipyridyl compounds,
typically prepared by alkylating at least one and preferably both
of the nitrogen atoms. Alkylation occurs by reacting the
above-described dipyridyl compounds with an alkylating agent. In
some embodiments, the alkylating agent may be of a type
particularly suitable for forming polymers. In some embodiments,
the alkylating agent is of a type that reacts with the dipyridyl
compound but does not form polymers.
[0107] Alkylating agents that are suitable for reacting with
dipyridyl compounds that generally form non-polymeric levelers may
have the general structure (34):
Y--(CH.sub.2).sub.o-A Structure (34)
wherein
[0108] A may be selected from among hydrogen, hydroxyl (--OH),
alkoxy (--OR.sub.1), amine (--NR.sub.2R.sub.3R.sub.4), glycol
##STR00020##
aryl
##STR00021##
and sulfhydryl or thioether (--SR.sub.14);
[0109] o is an integer between one and six, preferably one or two;
and
[0110] X is an integer from one to about four, preferably one or
two; and
[0111] Y is a leaving group. The leaving group may be selected from
among, for example, chloride, bromide, iodide, tosyl, triflate,
sulfonate, mesylate, dimethyl sulfonate, fluorosulfonate, methyl
tosylate, brosylate, or nosylate.
[0112] In each A group above, the single line emanating from the
functional moiety denotes a bond between an atom in the A moiety,
e.g., oxygen, nitrogen, or carbon, and a carbon of the
--(CH.sub.2).sub.o-- akylene group. Additionally, the R.sub.1
through R.sub.14 groups denoted in the A moieties of Structure (34)
are independently hydrogen; substituted or unsubstituted alkyl
having from one to six carbon atoms, preferably one to three carbon
atoms; substituted or unsubstituted alkylene having from one to six
carbon atoms, preferably from one to three carbon atoms; or
substituted or unsubstituted aryl. The alkyl may be substituted
with one or more of the following substituents: halogen,
heterocyclo, alkoxy, alkenoxy, alkynoxy, aryloxy, hydroxy,
protected hydroxy, hydroxycarbonyl, keto, acyl, acyloxy, nitro,
amino, amido, nitro, phosphono, cyano, thiol, ketals, acetals,
esters and ethers. In general, the various alkyl R groups are
hydrogen or unsubstituted alkyl.
[0113] With regard to the aryl group, any of the R.sub.6 through
R.sub.10 carbons, together with an adjacent R group and the carbons
to which they are bonded may form an aryl group, i.e., the aryl
group comprises a fused ring structure, such as a naphthyl
group.
[0114] Exemplary A groups include:
[0115] hydrogen,
[0116] hydroxyl (--OH),
[0117] methoxy (--OCH.sub.3),
[0118] ethoxy (--OCH.sub.2CH.sub.3),
[0119] propoxy (--OCH.sub.2CH.sub.2CH.sub.3 or
##STR00022##
[0120] amino (--NH.sub.2),
[0121] methylamino (--NHCH.sub.3),
[0122] dimethylamino
##STR00023##
[0123] ethylene glycol (--O--CH.sub.2CH.sub.2--OH),
[0124] diethylene glycol
##STR00024##
[0125] propylene glycol (--OCH.sub.2CH.sub.2CH.sub.2--OH or
##STR00025##
[0126] dipropylene glycol
##STR00026##
[0127] phenyl
##STR00027##
[0128] naphthenyl and
##STR00028##
[0129] sulfhydryl (--SH), or derivatives of each of these.
[0130] Preferably, A is selected from among:
[0131] hydrogen,
[0132] hydroxyl (--OH),
[0133] methoxy (--OCH.sub.3),
[0134] ethoxy (--OCH.sub.2CH.sub.3),
##STR00029##
[0135] propoxy (--OCH.sub.2CH.sub.2CH.sub.3 or
[0136] ethylene glycol (--OCH.sub.2CH.sub.2--OH),
[0137] diethylene glycol
##STR00030##
[0138] propylene glycol (--OCH.sub.2CH.sub.2CH.sub.2OH or
##STR00031##
[0139] phenyl
##STR00032##
and
[0140] naphthenyl
##STR00033##
[0141] or derivatives of each of these.
[0142] More preferably, A is selected from among:
[0143] hydroxyl (--OH),
[0144] ethylene glycol (--O--CH.sub.2CH.sub.2--OH),
[0145] propylene glycol (--OCH.sub.2CH.sub.2CH.sub.2OH or
##STR00034##
[0146] and
[0147] phenyl
##STR00035##
[0148] or derivatives of each of these.
[0149] Preferably, in the alkylating agents of Structure (34), o is
one or two, and Y is chloride.
[0150] Alkylating agents that react with the dipyridyl compounds
and generally form polymeric compounds may have the general
structure (35):
Y--(CH.sub.2).sub.p--B--(CH.sub.2).sub.q--Z Structure (35)
wherein
[0151] B may be selected from among:
[0152] a single bond, an oxygen atom (--O--), a methenyl
hydroxide
##STR00036##
a carbonyl
##STR00037##
an amino
##STR00038##
an imino
##STR00039##
a sulfur atom (--S--), a sulfoxide
##STR00040##
a phenylene
##STR00041##
and a glycol
##STR00042##
and
[0153] p and q may be the same or different, are integers between 0
and 6, preferably from 0 to 2, wherein at least one of p and q is
at least 1;
[0154] X is an integer from one to about four, preferably one or
two; and
[0155] Y and Z are leaving groups. The leaving group may be
selected from among, for example, chloride, bromide, iodide, tosyl,
triflate, sulfonate, mesylate, methosulfate, fluorosulfonate,
methyl tosylate, brosylate, or nosylate.
[0156] In each B group above, the single line emanating from the
functional moiety denotes a bond between an atom in the B moiety,
e.g., oxygen, nitrogen, or carbon, and a carbon of the
--(CH.sub.2).sub.p-- and --CH.sub.2).sub.q-- akylene groups.
Additionally, the R.sub.1 through R.sub.14 groups in denoted in the
B moieties of Structure (35) are independently hydrogen;
substituted or unsubstituted alkyl having from one to six carbon
atoms, preferably one to three carbon atoms; substituted or
unsubstituted alkylene having from one to six carbon atoms,
preferably from one to three carbon atoms; or substituted or
unsubstituted aryl. The alkyl may be substituted with one or more
of the following substituents: halogen, heterocyclo, alkoxy,
alkenoxy, alkynoxy, aryloxy, hydroxy, protected hydroxy,
hydroxycarbonyl, keto, acyl, acyloxy, nitro, amino, amido, nitro,
phosphono, cyano, thiol, ketals, acetals, esters and ethers. In
general, the various R groups are hydrogen or unsubstituted alkyl,
and even more preferably, the R groups are hydrogen.
[0157] Preferably, B is selected from among:
[0158] an oxygen atom (--O--),
[0159] a methenyl hydroxide
##STR00043##
[0160] a carbonyl
##STR00044##
[0161] a phenylene group
##STR00045##
[0162] an ethylene glycol group
##STR00046##
[0163] a propylene glycol group
##STR00047##
[0164] More preferably, B is selected from among:
[0165] an oxygen atom (--O--),
[0166] a methenyl hydroxide
##STR00048##
[0167] a carbonyl
##STR00049##
[0168] a phenylene group and
##STR00050##
[0169] an ethylene glycol group
##STR00051##
[0170] Preferably, in the alkylating agents of Structure (35), p
and q are both one or are both two, and Y and Z are both
chloride.
[0171] Another class of alkylating agents that may form a polymeric
leveler when reacted with the dipyridyl compounds includes an
oxirane ring and has the general structure (36):
##STR00052##
[0172] wherein
[0173] R.sub.11, R.sub.12, and R.sub.13 are hydrogen or substituted
or unsubstituted alkyl having from one to six carbon atoms,
preferably from one to three carbon atoms;
[0174] o is an integer between one and six, preferably one or two;
and
[0175] Y is a leaving group. The leaving group may be selected from
among, for example, chloride, bromide, iodide, tosyl, triflate,
sulfonate, mesylate, methosulfate, fluorosulfonate, methyl
tosylate, brosylate, or nosylate.
[0176] Preferably, R.sub.11, R.sub.12, and R.sub.13 are hydrogen
and the alkylating agent has the following general structure
(37):
##STR00053##
wherein o and Y are as defined in connection with Structure
(36).
[0177] Preferably, o is one, Y is chloride, and the alkylating
agent of general Structure (36) is epichlorohydrin.
The reaction product causes the leaving group to form an anion in
the reaction mixture. Since chloride is commonly added to
electrolytic copper plating compositions, Y and Z are preferably
chloride. While the other leaving groups may be used to form the
leveling compounds of the present invention, these are less
preferred since they may adversely affect the electrolytic plating
composition. Leveling agents that are charge balanced with, for
example, bromide or iodide, are preferably ion exchanged with
chloride prior to adding the leveling compound to the electrolytic
copper plating compositions of the present invention.
[0178] Specific alkylating agents of the above structure (34)
include, for example, 2-chloroethylether, benzyl chloride,
2-(2-chloroethoxy)ethanol, chloroethanol,
1-(chloromethyl)-4-vinylbenzene, and
1-(chloromethyl)naphthalene.
[0179] Specific alkylating agents of the above structure (35)
include, for example, 1-chloro-2-(2-chloroethoxy)ethane,
1,2-bis(2-chloroethoxy)ethane, 1,3-dichloropropan-2-one,
1,3-dichloropropan-2-ol, 1,2-dichloroethane, 1,3-dichloropropane,
1,4-dichlorobutane, 1,5-dichloropentane, 1,6-dichlorohexane,
1,7-dichloroheptane, 1,8-dichlorooctane,
1,2-di(2-chloroethyl)ether, 1,4-bis(chloromethyl)benzene,
m-di(chloromethyl)benzene, and o-di(chloromethyl)benzene.
[0180] A specific alkylating agent of the above structure (36) is
epichlorohydrin. The alkylating agents may comprise bromide,
iodide, tosyl, triflate, sulfonate, mesylate, dimethyl sulfonate,
fluorosulfonate, methyl tosylate, brosylate, or nosylate
derivatives of the above chlorinated alkylating agents, but these
are less preferred since chloride ion is typically added to
electrolytic copper plating compositions, and the other anions may
interfere with copper deposition.
[0181] A wide variety of leveler compounds may be prepared from the
reaction of the dipyridyl compounds having the structures (18)
through (33) and the alkylating agents having the general
structures (34) through (37). Reactions to prepare the leveler
compounds may occur according to the conditions described in Nagase
et al., U.S. Pat. No. 5,616,317, the entire disclosure of which is
hereby incorporated as if set forth in its entirety. In the
reaction, the leaving groups are displaced when the nitrogen atoms
on the pyridyl rings react with and bond to the methylene groups in
the dihalogen compound. Preferably, the reaction occurs in a
compatible organic solvent, preferably having a high boiling point,
such as ethylene glycol or propylene glycol.
[0182] In some embodiments, the leveler compounds of the present
invention are polymers, and the levelers may be prepared by
selecting reaction conditions, i.e., temperature, concentration,
and the alkylating agent such that the dipyridyl compound and
alkylating agent polymerize, wherein the repeat units of the
polymer comprise one moiety derived from the dipyridyl compound and
one moiety derived from the alkylating. In some embodiments, the
dipyridyl compound has the structure (27) and the alkylating agent
has the general structure depicted above in Structure (35). In some
embodiments, therefore, the leveler compound is a polymer
comprising the following general structure (38):
##STR00054##
wherein B, m, p, q, Y, and Z are as defined with regard to
structures (27) and (35), and X is an integer that is at least 2.
Preferably, X ranges from 2 to about 100, such as from about 2 to
about 50, from about 2 to about 25, and even more preferably from
about 4 to about 20.
[0183] As stated above, preferred dipyridyl compounds are based on
4,4'-dipyridyl compounds. In some preferred embodiments, the
leveler compound is a reaction product of 4,4'-dipyridyl of
structure (31) and an alkylating agent of structure (35). Reaction
conditions, i.e., temperatures, relative concentrations, and choice
of alkylating agent may be selected such that 4,4'-dipyridyl and
the alkylating agent polymerize, wherein the repeat units of the
polymer comprise one moiety derived from 4,4'-dipyridyl and one
moiety derived from the alkylating agent. In some embodiments,
therefore, the leveler compound is a polymer comprising the
following general structure (39):
##STR00055##
wherein B, p, q, Y, and Z are as defined with regard to structure
(35), and X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0184] One particular leveler compound in the class of levelers of
structure (39) is the reaction product of the 4,4'-dipyridyl and an
alkylating agent wherein B is the oxygen atom, p and q are both 2,
and Y and Z are both chloride, i.e.,
1-chloro-2-(2-chloroethoxy)ethane. This leveler compound is a
polymer comprising the following structure (40):
##STR00056##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0185] In some preferred embodiments, the leveler compound is a
reaction product of 4,4'-dipyridyl of structure (32) and an
alkylating agent of structure (35). Reaction conditions, i.e.,
temperatures, relative concentrations, and choice of alkylating
agent may be selected such that 4,4'-ethylenedipyridine and the
alkylating agent polymerize, wherein the repeat units of the
polymer comprise one moiety derived from 4,4'-ethylenedipyridine
and one moiety derived from the alkylating agent. In some
embodiments, therefore, the leveler compound is a polymer
comprising the following general structure (41):
##STR00057##
wherein B, p, q, Y, and Z are as defined with regard to structure
(35) and X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0186] One particular leveler compound in the class of levelers of
structure (41) is polymer that may be prepared from reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
oxygen atom, p and q are both 2, and Y and Z are both chloride,
i.e., 1-chloro-2-(2-chloroethoxy)ethane. This leveler compound is a
polymer comprising the following structure (42):
##STR00058##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20. In one
preferred leveler of structure (42), X is an average value from
about 3 to about 12, such as between about 4 and about 8, or even
about 5 to about 6. In one preferred leveler of structure (42), X
is an average value from about 10 to about 24, such as between
about 12 to about 18, or even about 13 to about 14.
[0187] Another leveler compound in the class of levelers of
structure (41) is a polymer that may be prepared by reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
ethylene glycol, p and q are both 2, and Y and Z are both chloride,
i.e., 1,2-bis(2-chloroethoxy)ethane. This leveler compound is a
polymer comprising the following structure (43):
##STR00059##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0188] Another leveler compound in the class of levelers of
structure (41) is a polymer that may be prepared by reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
carbonyl, p and q are both 1, and Y and Z are both chloride, i.e.,
1,3-dichloropropan-2-one. This leveler compound is a polymer
comprising the following structure (44):
##STR00060##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0189] Another leveler compound in the class of levelers of
structure (41) is a polymer that may be prepared by reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
methenyl hydroxide, p and q are both 1, and Y and Z are both
chloride, i.e., 1,3-dichloropropan-2-ol. This leveler compound is a
polymer comprising the following structure (45):
##STR00061##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0190] Another leveler compound in the class of levelers of
structure (41) is a polymer that may be prepared by reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
phenylene, p and q are both 1, and Y and Z are both chloride, i.e.,
1,4-bis(chloromethyl)benzene. This leveler compound is a polymer
comprising the following structure (46):
##STR00062##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0191] In some preferred embodiments, the leveler compound is a
reaction product of 4,4'-dipyridyl of structure (33) and an
alkylating agent of structure (35). Reaction conditions, i.e.,
temperatures, relative concentrations, and choice of alkylating
agent may be selected such that 1,3-di(pyridin-4-yl)propane and the
alkylating agent polymerize, wherein the repeat units of the
polymer comprise one moiety derived from
1,3-di(pyridin-4-yl)propane and one moiety derived from the
alkylating agent. In some embodiments, therefore, the leveler
compound is a polymer comprising the following general structure
(47):
##STR00063##
wherein B, p, q, Y, and Z are as defined with regard to structure
(35) and X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20.
[0192] One particular leveler compound in the class of levelers of
structure (47) is polymer that may be prepared from reacting
1,3-di(pyridin-4-yl)propane and an alkylating agent wherein B is
the oxygen atom, p and q are both 2, and Y and Z are both chloride,
i.e., 1-chloro-2-(2-chloroethoxy)ethane. This leveler compound is a
polymer comprising the following structure (48):
##STR00064##
wherein X is an integer of at least 2, preferably from 2 to 100,
such as from 2 to 50, and more preferred from 3 to about 20, such
as from about 4 to about 8, or from about 12 to about 16. In one
preferred leveler of structure (48), X is an average value from
about 5 to about 6. In one preferred leveler of structure (48), X
is an average value from about 13 to about 14.
[0193] In some embodiments, the leveler compounds may be prepared
by reacting a dipyridyl compound having the structure (27) and an
alkylating agent having the general structure depicted above in
Structure (35) in a manner that does not form a polymeric leveler.
That is, the levelers may be prepared by selecting reaction
conditions, i.e., temperature, concentration, in which the
alkylating agent such that the dipyridyl compound and alkylating
agent react but do not polymerize. The leveler compound may
comprise the following structure (49):
##STR00065##
wherein B, m, p, q, Y, and Z are as defined with regard to
structures (27) and (35).
[0194] As stated above, preferred dipyridyl compounds have general
structure (27) such that preferred levelers are based on
4,4'-dipyridyl compounds. In some preferred embodiments, the
leveler compound is a reaction product of 4,4'-dipyridyl of
structure (31) and an alkylating agent of structure (35) and may
comprise the following structure (50):
##STR00066##
wherein B, p, q, Y, and Z are as defined with regard to Structure
(35).
[0195] One particular leveler compound in the class of levelers of
structure (50) is the reaction product of the 4,4'-dipyridyl and an
alkylating agent wherein B is the oxygen atom, p and q are both 2,
and Y and Z are both chloride, i.e.,
1-chloro-2-(2-chloroethoxy)ethane. This leveler compound may
comprise the following structure (51):
##STR00067##
[0196] In some preferred embodiments, the leveler compound is a
reaction product of 4,4'-dipyridyl of structure (32) and an
alkylating agent of structure (35). In some embodiments, therefore,
the leveler compound may comprise the following structure (52):
##STR00068##
wherein B, p, q, Y, and Z are as defined with regard to structure
(35).
[0197] One particular leveler compound in the class of levelers of
structure (52) is the reaction product of the
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
oxygen atom, p and q are both 2, and Y and Z are both chloride,
i.e., 1-chloro-2-(2-chloroethoxy)ethane. This leveler compound may
comprise the following structure (53):
##STR00069##
[0198] Another leveler compound in the class of levelers of
structure (52) is a polymer that may be prepared by reacting
4,4'-ethylenedipyridine and an alkylating agent wherein B is the
ethylene glycol, p and q are both 2, and Y and Z are both chloride,
i.e., 1,2-bis(2-chloroethoxy)ethane. This leveler compound may
comprise the following structure (54):
##STR00070##
[0199] In some embodiments, the leveler compound may be prepared by
reacting a dipyridyl molecule having the structure (27) and an
alkylating agent having the general structure depicted above in
structure (34). This leveler compound may comprise the following
structure (55):
##STR00071##
wherein A, m, o, and Y are as defined with regard to structures
(27) and (34).
[0200] In some preferred embodiments, the leveler compound is a
reaction product of 4,4'-dipyridyl of structure (32) and an
alkylating agent of structure (34). In some embodiments, therefore,
the leveler compound may comprise the following structure (56):
##STR00072##
wherein A, o, and Y are as defined with regard to structure
(34).
[0201] One particular leveler compound in the class of levelers of
structure (56) is the reaction product of the
4,4'-ethylenedipyridine and an alkylating agent wherein A is the
phenyl group, o is 1, and Y is chloride, i.e., benzyl chloride.
This leveler compound may comprise the following structure
(57):
##STR00073##
[0202] The leveler concentration may range from about 1 ppm to
about 100 ppm, such as between about 2 ppm to about 50 ppm,
preferably between about 2 ppm and about 20 ppm, more preferably
between about 2 ppm and about 10 ppm, such as between about 5 ppm
and about 10 ppm.
wetting of the vias with the Cu filling chemistry. An exemplary
solution useful for degassing the wafer surface if MICROFAB.RTM. PW
1000, available from Enthone Inc. (West Haven, Conn.). After
degassing, TSV features located in the wafer is copper metallized
using the electrolytic copper deposition composition of the present
invention.
[0203] The exact configuration of the plating equipment is not
critical to the invention. If line power is used for the
electrolysis, the electrolytic circuit includes a rectifier for
converting the alternating current to direct current and a
potentiostat by which the polarity of the electrodes may be
reversed and the applied potential controlled to achieve the
current pattern utilized in the process of the invention. A
membrane separator may be used to divide the chamber containing the
electrolytic solution into an anode chamber in which a portion of
the electrolytic solution comprising an anolyte is in contact with
the anode and a cathode chamber in which a portion of the
electrolytic solution comprising a catholyte is in contact with the
metalizing surface, which functions as the cathode during the
forward current plating process. The cathode and anode may be
horizontally or vertically disposed in the tank.
[0204] During operation of the electrolytic plating system, copper
metal is plated on the surface of a cathode substrate when the
power source is energized and power directed through the rectifier
to the electrolytic circuit. The bath temperature is typically
between about 15.degree. and about 60.degree. C., preferably
between about 35.degree. and about 45.degree. C. It is preferred to
use an anode to cathode ratio of about 1:1, but this may also vary
widely from about 1:4 to 4:1. The process also uses mixing in the
electrolytic plating tank which may be supplied by agitation or
preferably by the circulating flow of recycle electrolytic solution
through the tank.
* * * * *